170 ANATOMY OF VERTEBRATES. 



sions of the second, third, and fourth lumbar nerves. Some of the 

 ventral branches pierce the intertransversalis before penetrating 

 the fascia of the psoas, on their way to the oblique and straight 

 abdominal muscles ; but the main proportion is taken by the 

 psoas. Anterior branches from the seventh, eighth, and ninth 

 lumbar nerves diverge from the ordinary course or distribution, 

 and partially unite with a plexus extending to and supplying the 

 muscles which connect the ischial or pelvic bones with the abdo- 

 minal and caudal muscles and those of the attached parts of the 

 sexual organs. The above nerves evidently represent the lumbar 

 plexus developed in Quadrupeds for the hind-limbs, but their 

 chief distribution is as ( pudenda! ' nerves. The anterior or 

 ventral divisions of the caudal nerves mainly combine to form a 

 nerve-trunk on that aspect of the tail, which is resolved into 

 many small parallel transverse branches, from which are supplied 

 the muscles and teguments of that part of the tail. The dorsal 

 divisions are similarly distributed, but only a very small propor- 

 tion goes to the skin. 1 



In the Ungulate series the distribution of the spinal nerves has 

 been followed by the hippotomists in the Horse and Cow; by 

 Swan in the Ass ; 2 and I have made observations on that part 

 of the anatomy of the Rhinoceros and Giraffe. 



Several branches from the superior cervical ganglion of the 

 sympathetic join, in a plexiform manner, the anterior division of 

 the first cervical ; this also receives a filament from the descendens 

 noni, which previously communicates either with the trunk or a 

 filament from the par vagum ; afterwards it joins the pharyngeal 

 plexus, and is distributed to the steruo-hyoid and sterno-thyroid 

 muscles. The nerve given to the serratus magnus proceeds 

 from the sixth cervical with the phrenic ; but the phrenic after- 

 Avards communicates with a branch of the seventh, given to the 

 pectoralis major. The axillary plexus in the Ass, also in the Pig, 

 is formed from the seventh cervical and the first and second dorsal 

 nerves. The superior scapular nerve proceeds chiefly from the 

 seventh cervical ; but in some degree from the first dorsal, and is 

 sent to the supra- and infra-spinati muscles of the scapula. Branches 

 proceeding from all the nerves forming the plexus are given to 



1 SWAN well notes the difference between the mode of supply to the natatory tail, 

 i.e. by a few trunks in Cetacea derived from a remotely situated myelon, and that in 

 Fishes, by many nerve-pairs from a contiguous myelon: also the great proportion of 

 motory as compared with sensory filaments ; the tail being not only the main motive 

 instrument in Whales, but capable of ' giving hard blows without feeling much pain.' 

 LIV. p. 165. 



2 LIV, 2d ed. pp. 153, et. seq. 



